Aquifer Thermal Energy Storage

Nearly all buildings and greenhouses of Wageningen University & Research on Wageningen Campus will eventually use Heat Cold Storage (ATES) for heating and cooling. ATES ultimately provides WUR with enormous energy savings without significant CO2 emissions. The pumps do use electricity, but WUR uses its own produced green electricity for this.

Principle of Aquifer Thermal Energy Storage

Aquifer Thermal Energy Storage is a sustainable energy supply in which heat and cold are stored via a heat exchanger (counter-current device, TSA) in a water-carrying sand package 90 meters deep in the ground. In summer a building is cooled with groundwater from the cold wells. And in winter a building is heated via the same heat exchanger, but now in combination with a heat pump, with groundwater from the warmth well. The heated water from the cold wells is stored in the warmth wells and the cooled water from the warmth wells in the cold wells. Both the cold and the warmth wells are interconnected with a loop.

WUR aims to save more than 1.3 million cubic meters of natural gas by constructing the wells and the induction loops. This corresponds to a reduction of approximately 2,400 tons of CO2 per year, comparable to the annual emissions of approximately 900 gas-consuming households.

Figure 1. Schematic ATES system
Figure 1. Schematic ATES system

The groundwater is therefore pumped back and forth between the cold well and the warmth well. On the left the situation with a cooling demand and on the right with a heating demand.

ATES on Wageningen Campus

Warmth and cold wells cannot be drilled directly next to each other. That is why three underground temperature streets have been realized in the aquifer sand package under the campus. Two smaller cold zones at the edges and a warmth zone in the middle. These are actually a kind of batteries, where we store warmth or cold from buildings deep underground for reuse. In total there are nine wells in the cold zones and nine in the warm zone. The buildings are then connected to two induction loops connecting the wells. The ATES loop plus a number of new wells were constructed in 2020-2021.

Figure 2. Warm and cold streets with the wells (including 6 future wells) on Wageningen Campus
Figure 2. Warm and cold streets with the wells (including 6 future wells) on Wageningen Campus

Reversible temperature transfer

We pump the warm water to the building if there is a need for heating. Every connected building has a heat exchanger that transfers the warmth from the groundwater, about 14-16 degrees, to the water of the internal building installation. It then pumps it to a heat pump. The heat pump then extracts the warmth and cools the water from the building installation back to about 5 degrees. The heat pump thus raises the water temperature to approximately 55 degrees for heating the building. The cooled water then returns to the heat exchanger which then pumps it back into the cold well.

When there is a need for cooling, the process runs in reverse. We then pump water of 7-8 degrees from the cold well. The use of the heat pump is not necessary in the cooling process.

During the season, the cold well warms up slightly and the warmth well cools down slightly. As a result, the temperature of the water that we pump from the wells is not the same all year round. However, the absolute temperature difference between the two zones remains fairly constant.